Medical implants for placement in a human or other animal body are well known in the art. One class of medical implants comprises endoluminal devices such as stents, stent-grafts, filters, coils, occlusion baskets, valves, and the like. As is known in the art, a stent is typically an elongated device used to support an intraluminal wall. Such a stent may also have a prosthetic graft layer of fabric or covering lining the inside and/or outside thereof. Such a covered stent is commonly referred to in the art as an intraluminal prosthesis, an endoluminal or endovascular graft (EVG), or a stent-graft. Although stent-grafts may be used in any number of applications, the use of stent-grafts for repairing abdominal aortic aneurysms (AAA) is an area of particular interest. Other devices, such as filters or occlusion devices (also known as wire clusters), may have similar structures to stents and may be placed in a body lumen by similar methods. As used herein, the term “endoluminal device” refers to covered and uncovered stents, filters, wire clusters, and any other device that may be placed in a lumen. The term “stent” as used herein is a shorthand reference referring to a covered or uncovered stent. Typical mechanisms for expansion of endoluminal devices include spring elasticity, balloon expansion, and self-expansion of a thermally or stress-induced return of a memory material to a pre-conditioned expanded configuration.
Endoluminal devices are sometimes coated on their outer surfaces with a substance such as a drug releasing agent, growth factor, or the like. U.S. Pat. No. 5,500,013 to Buscemi et al. is just one example of numerous patents relating to endoluminal devices having such coatings. Stents have also been developed comprising a hollow tubular wire with perforations for injecting drugs into the hollow wire and through the perforations into the body lumen, such as are disclosed by Leone et al. in U.S. Pat. No. 5,882,335 and U.S. Pat. No. 5,891,108, incorporated herein by reference.
Traditionally, an endoluminal device, such as a stent-graft deployed in a blood vessel at the site of a stenosis or aneurysm, is implanted endoluminally, i.e. by so-called “minimally invasive techniques” in which the device, restrained in a radially compressed configuration by a sheath or catheter, is delivered by a delivery system or “introducer” to the site where it is required. The introducer may enter the body from an access location outside the body, such as through the patient's skin (percutaneous methods), or by a “cut down” technique in which the entry blood vessel is exposed by minor surgical means. The term “proximal” as used herein refers to portions of the stent or delivery system relatively closer to the end of the delivery system extending outside of the body, whereas the term “distal” is used to refer to portions relatively farther from this outside end. When the introducer has been threaded into the body lumen to the deployment location, the introducer is manipulated to cause the endoluminal device to be ejected from the surrounding sheath or catheter in which it is restrained (or alternatively the surrounding sheath or catheter is retracted from the endoluminal device), whereupon the endoluminal device expands to a predetermined diameter at the deployment location, and the introducer is withdrawn.
Over the past several years there has been a drive toward developing low-profile endoluminal devices that can be introduced using the more preferred percutaneous approach, as the cut down approach has been found to have increased risk of complication associated with it. Thus, there is a continued need in the art for developing endoluminal devices having the lowest-possible profile and having as many positive attributes as possible.